We bear witness this week both to an international tragedy and to the largest architectural disaster in U.S. history. Five years ago, two of our largest buildings were utterly and unexpectedly destroyed, killing thousands of people who were unable to escape them. On this anniversary, as people around the world can still feel the ground reverberating, let us pause in remembrance.

As serious controversy continues around the geopolitical and military implications of the attack on the twin towers, naive controversy swirls around the structural mechanisms of collapse. Confusion, unseemly power-brokering, and erratic steps seem also to characterize the reconstruction planning process.

Still, the complex gears of that process have been turning, and designs for a set of new towers have just been unveiled. We present images of those designs, but will leave the critical appraisal they deserve for a later time.

Another compact but important controversy turns around the sole architectural fragment of the two towers, a stepped and scarred wedge of concrete which has become known as the "Survivors Staircase." Listed by the National Trust for Historic Preservation among America's 11 Most Endangered Historic Places for 2006, it too would be demolished according to the latest reconstruction plans. The reasons to save the stairway are nothing but symbolism and memory — which combined are surely the very essence of memorial. >>>